build: add OVERRIDE_VERSION, used in Travis

Fixes https://github.com/awesomeWM/awesome/issues/160.

.travis.yml

@@ -90,6 +90,9 @@ install:
   # Deps for functional tests.
   - sudo apt-get install -qq dbus-x11 xterm xdotool xterm xvfb
 
+  # Determine custom version.
+  - '[ "$TRAVIS_PULL_REQUEST" = false ] && version="${TRAVIS_BRANCH}-g$(git rev-parse --short HEAD)-$(date -Iseconds)" || version="${TRAVIS_BRANCH}-PR${TRAVIS_PULL_REQUEST}-g$(git rev-parse --short HEAD)-$(date -Iseconds)"'
+
 script:
-  - export CMAKE_ARGS="-DLUA_LIBRARY=${LUALIB} -DLUA_INCLUDE_DIR=/usr/include/lua${LUAPKG}"
+  - export CMAKE_ARGS="-DLUA_LIBRARY=${LUALIB} -DLUA_INCLUDE_DIR=/usr/include/lua${LUAPKG} -D OVERRIDE_VERSION=$version"
   - make && sudo env PATH=$PATH make install && awesome --version && tests/run.sh

awesomeConfig.cmake

@@ -89,14 +89,16 @@ endif()
 # }}}
 
 # {{{ Version stamp
-if(EXISTS ${SOURCE_DIR}/.git/HEAD AND GIT_EXECUTABLE)
+if(OVERRIDE_VERSION)
+    set(VERSION ${OVERRIDE_VERSION})
+elseif(EXISTS ${SOURCE_DIR}/.git/HEAD AND GIT_EXECUTABLE)
     # get current version
     execute_process(
         COMMAND ${GIT_EXECUTABLE} describe --dirty
         WORKING_DIRECTORY ${SOURCE_DIR}
         OUTPUT_VARIABLE VERSION
         OUTPUT_STRIP_TRAILING_WHITESPACE)
-    # file the git-version-stamp.sh script will look into
+    # File the build-utils/git-version-stamp.sh script will look into.
     set(VERSION_STAMP_FILE ${BUILD_DIR}/.version_stamp)
     file(WRITE ${VERSION_STAMP_FILE} ${VERSION})
     # create a version_stamp target later